1. Field of the Invention
The invention is directed to a locking block screw connection for spectacle mounts.
2. Description of the Prior Art
Different construction forms are known for the problem of preventing the loosening of screws. For example, it has been attempted to increase protection against the loosening of screws by means of clamping in that knurling is arranged on the screw head or screw shank area. Variants of this kind do not achieve the required security, since the screws are not secured axially and can therefore loosen. Further, constructions are known in which plastic is injected around the head area or shank area of the screw in order to increase security. However, these variants cannot absorb rotational loosening forces and do not achieve genuine protection against loosening because of the inferior material strength of plastic, so that full protection is not realized in these variants.
Other variants are constructed with additional clamping sleeves, etc., but do not offer complete protection against loosening of the screw and can be produced only by considerable extra expenditure.
In a construction according to DE 37 37 126, improved security against loosening of the screw connection is achieved in that a collar is arranged at the screw head and in that material is pressed into this collar by plastic deformation. In proportion, however, enormously high plastic deforming forces and area friction forces act on the connection in this case, so that deformations can occur at the thread when screwing in as a result of high flank loading. The use of a securing connection brought about in a plastic manner cannot therefore achieve success in terms of function for metal materials.
In a construction according to EP 393244, increased protection against loosening by plastic clamping is achieved only in the conical screw head zone. The screw is not fully secured against loosening because the rotational loosening forces act on the screw and this screw can therefore loosen due to the absence of any real axial securing.
WO 95/32 448, FIGS. 2 and 3, discloses a screw protection for the frame connection in which the screw 2 has a continuation piece having a constant diameter before the screw thread in the screw direction, wherein an annular groove 7 is introduced in the continuation piece and a Seeger ring or snap ring 8 can be inserted into this annular groove 7 after the screw is screwed in.
The frame parts 1a, 1b are elastically supported relative to one another by a spring 5, 10. This construction has a relatively large number of structural component parts and, for technical reasons, requires the use of a Seeger ring or snap ring.
In U.S. Pat. No. 5,488,440, the screw for connecting the frame parts is secured in that the internal thread for receiving the screw is initially compressed elastically to the required diameter by screwing in and a clamping action is accordingly exerted on the screw.
In this connection, at least when the connection is used as a hinge connection, a constant position of the screw, i.e., the movability of the hinge, is not guaranteed.